Imaging various types of cancers is clinically important since early diagnosis most directly correlates with prognosis of a patient. For example, approximately 130,000 new cases of colorectal cancer are diagnosed each year in the United States. Thus colorectal cancer is the fourth most common cancer in the U.S., accounting for 60,000 deaths per year. Treatment depends primarily on the cancer stage, but may include surgery, radiation, and/or chemotherapy. Although the majority of patients can be treated with curative surgical resection of the primary tumor, between 10-75% of the patients recur, depending on the stage. At the time of recurrence, the most common site of metastases is the liver, followed by the lung. In patients with metastatic disease, surgery is the only potentially curative option and has become widely accepted for patients with isolated liver or lung metastases. However, even if resection is possible, the five-year survival is between 25-50% after complete resection of liver or lung metastases. Unfortunately, the majority of patients with metastatic disease are not candidates for surgery because of advanced disease. Although the median survival for patients with metastatic colorectal cancer has improved with modern chemotherapeutic regimens, these patients are not curable. Thus there is a need for earlier detection of metastatic disease by improving imaging modalities for staging patients with colorectal cancer.
Imaging plays an essential role both in staging patients at the time of diagnosis and evaluating for recurrence during follow-up. The standard imaging test to evaluate for metastases is a contrast-enhanced abdominal and pelvic CT scan. However, even with good quality dynamic CT, recurrences are rarely detected early enough to be amenable to curative resection. Clearly, in order for patients with metastatic disease to be candidates for curative resection, detecting the disease at an early stage is vital. Accordingly, there is a need for development of additional methods for detection of metastatic or recurrent diseases.